Mc Millan, Michigan Weather Forecast Discussion

486
FXUS63 KMQT 181824
AFDMQT
Area Forecast Discussion
National Weather Service Marquette MI
224 PM EDT Thu Sep 18 2025
.KEY MESSAGES...
- Isolated to scattered showers and thunderstorms possible
  tonight and Friday across western Upper Michigan.
- Seasonable temperatures through the weekend.
- Rain and thunderstorms chances exist through early next week.
&&
.DISCUSSION...
Issued at 223 PM EDT Thu Sep 18 2025
Early afternoon GOES satellite imagery reveal a closed upper low
placed atop the northern Plains with a few embedded shortwave
wobbles within the broad low. This is reflecting a ~1014 mb sfc low
pressure in eastern SD. Closer to home, the northern Great Lakes sit
under the western flank of an expansive ridge with sfc high pressure
nosing southward from the Hudson Bay down into Lake Superior. Weak
synoptic forcing has managed to kick off a few light showers across
the western UP and WI/UP border counties, though subsidence has kept
this precipitation confined to these areas and showers have largely
died out with and further eastern attempt.
Tonight, expecting similar conditions with mostly cloudy skies
though there may be an uptick in spotty shower activity in the far
western UP as one of the aforementioned embedded waves rotates around
the parent upper low and lifts into western WI by Friday morning.
Scattered spotty showers linger across the west through Friday.
Breezy east winds will keep temperatures seasonable tomorrow as well,
with day time highs approaching the mid 60s while the Keweenaw stays
closer to 60.
Saturday, ridging over the eastern CONUS begins to break down and
move off of the east coast, allowing the churning closed low over
the Plains to open up and head into the Great Lakes, sending in
waves of precipitation across the UP. Deterministic guidance is in
good agreement on a secondary trough swinging in behind the lifting
shortwave on Sunday, giving higher confidence that precip will
linger through the rest of the weekend and into early next week.
From there, deterministic guidance begins to differ on the upper air
pattern Mon/Tues and even more so on the potential development of a
closed low in the central US by midweek.
&&
.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 223 PM EDT Thu Sep 18 2025
Radar and satellite imagery show broken cloud cover and isolated to
scattered showers across the western half of the U.P. as of 18z Thu,
producing mainly VFR conditions with a few pockets of MVFR. Low
stratus and patchy fog has again been more stubborn to erode across
the central U.P., owing to persistent N-NE upslope flow in the low
levels. This has kept KSAW more in the IFR-MVFR range thus far
today. Going forward, expect gradual improvement towards VFR in most
area through 21z. Will carry a PROB30 group for thunderstorms and
MVFR cigs at KIWD after 00z Fri as shower activity mainly stays
confined to the western half of the area through the period. Could
see low clouds and fog develop again tonight at KSAW in the 06-10z
period, with latest hi-res guidance depicting a 50-60% chance for
MVFR conditions or lower.
&&
.MARINE...
Issued at 223 PM EDT Thu Sep 18 2025
Breezy NE winds 20-25 kts in the far western arm of Lake Superior
diminish to 15-20 kts tonight before coming back up tomorrow
afternoon between 25-30 kts out of the ENE mainly west of the
Keweenaw to Duluth. There, significant wave heights will build
between 4-8 feet north and west of the Apostle Islands. Gusty ENE
winds begin to veer ESE late Friday into early Saturday, focusing 25
kt gusts to the central and eastern lake. The highest wave heights
will be concentrated to Canadian waters and far northern lake shores.
ESE winds fall below 20 kts through Sunday becoming south below 15
kts by Sunday evening. Calm conditions return early next week.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
DISCUSSION...BW
AVIATION...CB
MARINE...BW

NWS MQT Office Area Forecast Discussion